Male age mediates reproductive investment and response to paternity assurance.

addresses: Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, , Cornwall Campus, Penryn TR10 9EZ, UK, Department of Genetics, University of Georgia, , Athens, GA 30602, USA.types: Journal ArticleTheory predicts that male response to reduced paternity will depend on male state and interactions between the sexes. If there is little chance of reproducing again, then males should invest heavily in current offspring, regardless of their share in paternity. We tested this by manipulating male age and paternity assurance in the burying beetle Nicrophorus vespilloides. We found older males invested more in both mating effort and parental effort than younger males. Furthermore, male age, a component of male state, mediated male response to perceived paternity. Older males provided more prenatal care, whereas younger males provided less prenatal care, when perceived paternity was low. Adjustments in male care, however, did not influence selection acting indirectly on parents, through offspring performance. This is because females adjusted their care in response to the age of their partner, providing less care when paired with older males than younger males. As a result offspring, performance did not differ between treatments. Our study shows, for the first time, that a male state variable is an important modifier of paternity-parental care trade-offs and highlights the importance of social interactions between males and females during care in determining male response to perceived paternity

Incipient Cognition Solves the Spatial Reciprocity Conundrum of Cooperation

Background: From the simplest living organisms to human societies, cooperation among individuals emerges as a paradox difficult to explain and describe mathematically, although very often observed in reality. Evolutionary game theory offers an excellent toolbar to investigate this issue. Spatial structure has been one of the first mechanisms promoting cooperation; however, alone it only opens a narrow window of viability. Methodology/Principal Findings: Here we equip individuals with incipient cognitive abilities, and investigate the evolution of cooperation in a spatial world where retaliation, forgiveness, treason and mutualism may coexist, as individuals engage in Prisoner’s Dilemma games. In the model, individuals are able to distinguish their partners and act towards them based on previous interactions. We show how the simplest level of cognition, alone, can lead to the emergence of cooperation. Conclusions/Significance: Despite the incipient nature of the individuals ’ cognitive abilities, cooperation emerges for unprecedented values of the temptation to cheat, being also robust to invasion by cheaters, errors in decision making an

Interpersonal Aggression among Aka Hunter-Gatherers of the Central African Republic

This paper explores sex differences in interpersonal aggression among Aka foragers of the Central African Republic (CAR). We tested whether male Aka physically aggressed more than female Aka, and whether female Aka indirectly aggressed more than male Aka, as evolutionary theories of aggression predict. To our knowledge, these are the first tests of these theories among an extant population of hunter-gatherers. We also tested predictions of a recent evolutionary theory of physical strength, anger, and physical aggression. Data include a measure of upper body strength, age, sex, and qualitative views on aggression norms, as well as peer assessments of anger, physical aggression, and indirect aggression. Our results provide mixed support for the predicted sex differences in physical aggression and indirect aggression, and for the predicted relationships among anger, strength, and the use of aggression